Interleukin-12 (IL-12) is a heterodimeric cytokine (p70) composed of two subunits (p35 and p40), and plays key roles in immune responses by bridging innate resistance and antigen-specific adaptive immunity. Trinchieri (1993) Immunol Today 14: 335. For example, it promotes type 1 T helper cell (Th1) responses and, hence, cell-mediated immunity. Chan et al. (1991) J Exp Med 173: 869; Seder et al. (1993) Proc Natl Acad Sci USA 90: 10188; Manetti et al. (1993) J Exp Med 177: 1199; and Hsieh et al. (1993) Science 260: 547. Overproduction of IL-12 causes excessive Th1 responses, and may result in inflammatory disorders, insulin-dependent diabetes mellitus, multiple sclerosis, rheumatoid arthritis, psoriasis, Crohn's disease, or sepsis. See, for example, Gately et al. (1998) Annu Rev Immunol. 16: 495; and Abbas et al. (1996) Nature 383: 787. Thus, inhibiting IL-12 overproduction is an approach to treat the just-mentioned diseases. Trembleau et al. (1995) Immmunol. Today 16: 383; and Adorini et al. (1997) Chem. Immunol. 68: 175. For example, overproduction of IL-12 and the resultant excessive Th1 type responses can be suppressed by modulating IL-12 production. A compound that down-regulates IL-12 production can be used for treating inflammatory diseases. Ma et al. (1998) Eur Cytokine Netw 9: 54.